Query for duplicates.

Greetings,

I found myself in an unusual situation today. I need a query to display
only customers with addresses that appear more than once. Usually I am
having to get unique addresses, etc. at which I have become very good, but
this one is giving me a run for.

What I need is something like this:

create table customer (
custdate date,
name varchar(30),
address varchar(30),
city varchar(20),
state varchar(2),
zip varchar(10));

select address,city,state,zip from customer
where custdate<='05-30-1999'
group by address having count(address)>1;

I know this does not work, but if it did it would have the results I am
looking for.

Thanks,
Matthew